I (Dan) have volunteered as an "Independent Visitor" for the last 6 years.
This involves being matched to a young person in care and taking them out on day trips, befriending them, being someone they can talk to and rely on. Often this might just be trips into town, to the library or cinema. However occasionally the charity is given funding that can see the young person having great new experiences that they may not otherwise be fortunate enough to have (Alton Towers / Go Karting / Driving Lesson / their own mountain bike!)
NYAS cover more than just the Independent Visitor activities, they also offer Advocacy for young people - being a voice for those who may not have one.